PROJECT SUMMARY/ABSTRACT There is a fundamental gap in understanding how to define and create a ?healthy? indoor microbial environment for the 300 million children and adults with asthma. There is a growing recognition that the indoor microbiome may impact asthma development and morbidity, yet the few available environmental microbiome studies in asthma suggest that microbial exposures such as microbial diversity are simultaneously beneficial for asthma prevention and harmful for asthma symptoms in children already diagnosed with asthma. The long- term goal is to create healthy indoor environments for children with asthma. The overall objective of this application is to investigate the contribution of the classroom microbiome to asthma morbidity and determine whether we can modify the indoor microbiome to reduce asthma symptoms by leveraging the infrastructure of the School Inner-City Asthma Intervention (SICAS-2) study, a randomized controlled trial conducted by our group of a comprehensive school-based integrated pest management (IPM) intervention combined with a placebo-controlled classroom high efficiency particulate air (HEPA) cleaner intervention to assess the impact of these environmental interventions on asthma morbidity. Our strong preliminary data supports the central hypothesis that the classroom microbiome is modifiable and affects asthma morbidity independent of allergen exposure through colonization. We will test the central hypothesis by pursuing three specific aims: 1) To determine the extent to which the classroom microbiome is modifiable by a randomized IPM and HEPA cleaner intervention, findings that may be relevant for other infectious and inflammatory diseases; 2) Identify specific classroom microbial features independently associated with asthma symptoms, including identifying joint and interaction effects with allergen exposure, findings that may lead to identification of specific microbial strains important for future environmental remediation efforts; 3) Estimate the effect of upper airway colonization by classroom-associated microbes on asthma symptoms and the host immune profile, an important aim that may lead to a paradigm shift for how we approach exposure mitigation for asthma symptoms, since changes to the human microbiome may persist after exposure cessation. The approach is innovative, because the study is in the school setting with a randomized environmental intervention, a robust design for human studies that allows for causal interpretations. The hypothesis tested departs from the status quo, which is largely focused on allergens and microbial toxins in the home setting. The proposed research is significant, because asthma affects 8.4% of children in the United States and is the leading cause of school absenteeism. Ultimately, such knowledge has the potential to lead to better future prevention and treatment strategies for chronic lung disease due to environmental microbial exposures.